1. Field of the Invention
The present invention relates to a variable attenuation type optical power attenuator used for an optical fiber communications system. More particularly, the invention relates to an optical power attenuator of a new variable attenuation type in which a pair of ferrules having optical fibers with end surfaces thereof formed to be inclined against a plane perpendicular to the optical axis are oppositely aligned coaxially in the hole of an alignment sleeve. One of the paired ferrules is rotated to change the distance between the optical fiber end surfaces so as to permit continuous change of optical power attenuation and to automatically fix and maintain any desired optical power attenuation position.
2. Description of the Related Art
Referring to FIG. 4A and FIG. 4B, the principle of variable optical power attenuation will be described. The inventor has already proposed an optical power attenuator of the variable attenuation type, which employs the principle, under U.S. Pat. No. 5,136,681. FIG. 4A is a sectional view illustrating a setting for a minimum optical power attenuation, while FIG. 4B is a sectional view illustrating a setting for a maximum optical power attenuation. A pair of ferrules 8 and 9 with optical fibers, the end surfaces of which are formed to be inclined at an angle xcex8 with respect to a surface perpendicular to the optical axis thereof, are oppositely aligned coaxially in the hole of an alignment sleeve 17. One of the ferrules, for example, the ferrule 9, is rotated to change a distance S between the end surfaces of the optical fibers so as to continuously vary the optical power attenuation.
There has been a strong demand for actually using the variable attenuation type optical power attenuator, which has been disclosed under U.S. Pat. No. 5,136,681, for an optical fiber communications circuit or the like of a CATV, etc. Putting this variable attenuation type optical power attenuator to practical use has been facing the following main technological task to be achieved. The variable attenuation type optical power attenuator has to permit easy adjustment or setting to a desired optical power attenuation value, and once the optical power attenuation value has been adjusted or set, this value must not be disturbed by an external force such as mechanical vibration or impact.
An object of the present invention is to provide a variable attenuation type optical power attenuator that has successfully achieved the task in the conventional variable attenuation type optical power attenuator with the rotating ferrule as set forth above.
It is a further specific object of the invention to provide a new variable attenuation type of optical power attenuator that allows the amount of optical power attenuation to be continuously changed and also enables a set optical power attenuation point to be automatically fixed and maintained. In this new variable attenuation type of variable optical power attenuator, a face ratchet of a ratchet ring installed on a fixed ferrule housing such that it may linearly move in the axial direction is automatically engaged with or disengaged from a face ratchet of a ratchet ring provided in association with a rotating ferrule housing by rotating the rotating housing.
It is another object of the invention to provide a variable attenuation type optical power attenuator with a latching ratchet that can be used as an FC type variable attenuation type optical power attenuator.
To these ends, according to one aspect of the invention, there is provided a variable attenuation optical power attenuator with a latching ratchet, including: a fixed ferrule and a rotating ferrule having the end surfaces thereof polished, together with central optical fibers thereof, to be formed into inclined surfaces; an alignment sleeve which receives the fixed and rotating ferrules with optical fibers in such a manner that the distal ends thereof are opposed to each other and the ferrules may be relatively rotated; a fixed housing which restricts the rotation of the fixed ferrule and which receives the alignment sleeve and the rotating ferrule; a rotating housing which has a face ratchet facing the fixed housing and which is joined by a threaded portioned portion such that it may rotationally move forward or backward in relation to the fixed housing while it is coupled to the fixed ferrule to restrict the rotation of the fixed ferrule; a ratchet ring which has its rotation restricted by the fixed housing, which is joined such that it may move forward or backward while being urged by a first spring toward the rotating housing, and which has a face ratchet engaging a face ratchet of the rotating housing; and a second spring provided between the rotating ferrule with the optical fiber and the rotating housing; wherein the rotating housing is rotated to change the relative rotational angle with respect to the fixed housing so as to adjust the distance between the optical fiber end surface of the fixed ferrule and that of the rotating ferrule.
According to another aspect of the invention, there is provided a variable attenuation type optical power attenuator with a latching ratchet, including: a pair of ferrules with optical fibers having the end surfaces thereof polished, together with the central optical fibers thereof, to be formed into inclined surfaces and which are respectively provided with flanges having engaging portions on the outer peripheries thereof; an alignment sleeve which receives the fixed and rotating ferrules with optical fibers in such a manner that the ends thereof are opposed to each other and the ferrules may be relatively rotated; a fixed housing which has an engaging portion which engages the flange of the fixed ferrule to restrict the rotation, a portion for receiving the alignment sleeve, a coupling threaded portion, and a rectilinear joining portion; a rotating housing which has a face ratchet having many (n) teeth, a threaded portion engaging the coupling threaded portion of the fixed housing, and an engaging portion which engages the engaging portion of the flange of the rotating ferrule with the optical fiber; a ratchet ring equipped with a face ratchet which engages the face ratchet of the rotating housing and a rectilinear joining portion which engages the rectilinear joining portion of the fixed housing; and first and second coil springs; wherein the fixed and rotating ferrules, which have been coupled by the alignment sleeve, are inserted in the fixed housing by joining the flange of the fixed ferrule to the rectilinear joining portion; the rotating housing is joined by a threaded portion to the fixed housing with the second coil spring inserted between the flange of the rotating ferrule with the optical fiber and the rotating housing; and the ratchet ring is engaged with the rectilinear joining portion of the fixed housing with the first coil spring inserted between the rotating housing and the ratchet ring, and the face ratchet is opposed to the face ratchet of the rotating housing.
In a preferred form of the variable attenuation optical power attenuator with the latching ratchet; each time the rotating housing is turned by 2xcfx80/2n, the ratchet ring automatically moves linearly in the axial direction along the surface of the face ratchet to disengage the face ratchets; and when the ratchet ring is brought back to a home position thereof by the coil spring to re-engage the face ratchets, the rotational angle of the rotating housing is shifted to adjust the optical power attenuation value on at a pitch of 1/N (N =Number of the teeth of each of the face ratchets), and the adjusted rotational angle can be fixed and maintained.
In another preferred form, the outer end surfaces of the fixed housing and the rotating housing are respectively provided with engaging portions such as threaded portions that engage optical connector plugs or optical connector adapters to constitute an FC variable attenuation type optical power attenuator with a latching ratchet.
In yet another preferred form, the face ratchets of the variable attenuation optical power attenuator with the latching ratchet may have ratchet teeth which have apex angles of about 60 degrees.
In a further preferred from, the engaging portions of the flanges of the ferrules may be axial grooves.
In a further preferred form, one or both of the optical fibers supported by the fixed ferrule and the rotating ferrule may be an attenuation optical fiber or fibers.
More specifically, the variable attenuation type optical power attenuator with a latching ratchet in accordance with the present invention is assembled as follows. One end surface of each of the two ferrules with optical fibers, to which flanges provided with detent means such as keyways on the outer diameter surfaces thereof are securely attached, is finished to be inclined at 4 degrees or more with respect to a surface perpendicular to the optical axis of the optical fibers. With the inclined end surfaces opposed to each other, the ferrules with the optical fibers are rotatably inserted in the hole of an alignment sleeve to make up a ferrule assembly with the optical fibers.
A key is fitted in a larger outer diameter surface of a stepped outside diameter surface and a coil spring is fitted in a smaller outer diameter surface; a key that engages the keyway of the flange of one of the ferrules with optical fibers is provided on the inner diameter surface; a hole in which the alignment sleeve is inserted is provided at the central part; and a fixed housing equipped with a threaded portion is provided on the other end surface. A face ratchet having at least 20 teeth and a threaded portion that engages the threaded portion of the fixed housing are provided on the outer diameter side. A key engaging the keyway of the flange of the other ferrule with the optical fiber is provided at the distal end of the threaded portion, and a rotating housing equipped with a back facing hole in the inner surface to house the coil spring therein is provided. A keyway engaging with the key on the outer diameter surface of the fixed housing is provided on one end surface of the outer diameter of the ratchet ring, a face ratchet which engages the face ratchet of the rotating housing is provided on the other end surface thereof, and a back facing hole in which the coil spring is inserted is provided in the inner diameter surface. The ratchet ring is fitted, together with the coil spring, to the outer diameter surface of the fixed housing so that the keyway of the ratchet ring engages the key provided on the outer diameter of the fixed housing. Further, the keyway of the flange of one of the ferrules of the ferrule assembly with optical fibers is engaged with the key on the inside diameter surface of the fixed housing. Then, the keyway of the flange of the other ferrule of the ferrule assembly with the optical fibers is engaged with the key on the end surface of the rotating housing, and the fixed housing and the rotating housing are coupled by an engaging threaded portion.
In the variable attenuation type optical power attenuator with the latching ratchet, each time the rotating housing is rotated by 1/2N (N =Number of the teeth), the ratchet ring automatically moves in the axial direction linearly along the surface of the face ratchet to disengage the face ratchets, and when the ratchet ring is brought back to its home position by the coil spring to re-engage the face ratchets, the rotational angle of the rotating housing is changed at the pitch of 1/N (N=Number of the teeth of the face ratchet) thereby to adjust the optical attenuation value. The newly set rotational angle can be fixed and maintained.